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RETENTION OF INSOLUBLE PARTICLES FOLLOWING LOCAL INTRABRONCHIAL DEPOSITION IN DOGS
Citation:
Lay, J., C. Berry, C. Kim, AND W. Benett. RETENTION OF INSOLUBLE PARTICLES FOLLOWING LOCAL INTRABRONCHIAL DEPOSITION IN DOGS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-96/047.
Description:
Recent studies have challenged the generally accepted hypothesis that bronchial particle clearance is complete within 24 to 48 hours post-deposition. e studied bronchial retention of inert particles, using a bronchoscope and microspray nozzle to localize deposition in a bronchus while avoiding alveolar deposition. ix-ul aliquots (444kBq) of submicron 99mTc-sulfur colloid (SC) particles (n=6) or the unbound radiolabel, 99mTc-pertechnetate (99mTcO4-,n=3), were sprayed onto a 5mm diameter bronclius in Halothane anesthetized dogs. adioactivity at the deposition site and clearance pathway was monitored externally with a gamma camera, beginning immediately post-spraying. ronchial retention of SC was 8.5 +/- 2.4% and 1.5 +/- 0.7%, respectively, at 3 and 24 hours post-spray. racheal mucus velocity was measured at 10.4 +/- 2.2 mm/minute. or comparison, clearance of inhaled SC was also measured in the same dogs. etention of inhaled aerosolized SC (peripheral lung deposition) was 98.1 +/- 1.1% and 76.3 +/- 1.8% at 3 and 24 hours, respectively. 9mTcO4- cleared from the bronchi slightly more rapidly than SC. Radioactivity was readily detected in the blood following deposition of 99mTcO4-but not SC. hus, SC cleared by mucociliary transport, while 99mTcO4-cleared predominantly by transepithelial absorption. e conclude that clearance of submicron particles from a 5mm conducing airway is very nearly complete by 24 hours, with approximately 92% of the clearance occurring within the first 3 hours post-deposition.